HelloMove all switches and controls while listening to see if the left gets louder. It often is just oxidation of switch contacts that will cause that and if your lucky spray cleaning them will clean it up. I suggest cleaning all controls anyways given the vintage of that receiver. I have a 400 and had to open up the switches to clean the silver contacts, not the easiest job to do but all the oxidation can be removed that way.

HelloMove all switches and controls while listening to see if the left gets louder. It often is just oxidation of switch contacts that will cause that and if your lucky spray cleaning them will clean it up. I suggest cleaning all controls anyways given the vintage of that receiver. I have a 400 and had to open up the switches to clean the silver contacts, not the easiest job to do but all the oxidation can be removed that way.

Please don't do a "recap". That type of service doesn't address the age of the unit and certainly doesn't look after some of the real issues that might crop up. Certainly, some capacitors will need replacement. Some capacitors will not need replacement. There will also be some resistors that will be way off value, and possibly issues like alignment to look at.

When cleaning controls, use as little cleaner as is humanly possible. Cleaners wash out the lubricants that protect the carbon track. The noise and contact issues come from the slip ring, not the carbon track! You need to get the cleaner into the slip ring area near the center of the control. It wouldn't hurt to put some fine, single weight, no detergent oil into the bearings for the shafts. 3-n-1 and sewing machine oils are not suitable. WD-40 is not a lubricant either.

BTW, WD-40 destroys rubber quickly. That means you have to keep it away from all capacitors and some transistors. Any fluid getting into tuning or trimmer capacitors is also a disaster. Same for the dial cord assembly. It's important to use as little as possible and to protect these other areas from contamination.

Yes, WD40 is a solvent not a lubricant. And the reality is, oil based lubricants can also destroy rubber over time ... something learned from spending decades working on vehicles. Just keep the lubricants on the metal parts where they're supposed to be and all will be good. Any 5 or 10 weight engine oil (ie 5w or 10w, not multi grade oil) will suffice ... it's the same as using 3 in 1, sewing machine oil, or tranny fluid, all of which are light weight oils (with some additives for their intended purpose, or just a scent with one of those products) in an expensive package.

To clarify, you need a fine, single weight oil with zero additives. If you look, you can find fine, instrument grade fine oils. I have some that is like water. It does a good job of wicking into bearings.

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